stdlib: Fix os.startfile (#10996)

Fixes #10991

stdlib/os/__init__.pyi

@@ -923,10 +923,16 @@ def times() -> times_result: ...
 def waitpid(__pid: int, __options: int) -> tuple[int, int]: ...
 
 if sys.platform == "win32":
-    if sys.version_info >= (3, 8):
-        def startfile(path: StrOrBytesPath, operation: str | None = None) -> None: ...
+    if sys.version_info >= (3, 10):
+        def startfile(
+            filepath: StrOrBytesPath,
+            operation: str = ...,
+            arguments: str = "",
+            cwd: StrOrBytesPath | None = None,
+            show_cmd: int = 1,
+        ) -> None: ...
     else:
-        def startfile(filepath: StrOrBytesPath, operation: str | None = None) -> None: ...
+        def startfile(filepath: StrOrBytesPath, operation: str = ...) -> None: ...
 
 else:
     def spawnlp(mode: int, file: StrOrBytesPath, arg0: StrOrBytesPath, *args: StrOrBytesPath) -> int: ...